1+1/6+2+1/12+3+1/20+4+1/30+5+1/42+6+1/56+7+1/72=1+2+3+4+5+6+7+(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9)=28+7/18